Dual-beam incandescent lamp



Feb. 3, 1970 T. A. c. JAco Bs ET AL ,80

DUAL'BEAM INCANDESCENT LAMP Filed Feb. 23, 1967 2 Sheets-Sheet 1 WWW/10110111 "IIII FIG. 2

Feb. 3, 1970 c, JACOBS ET AL. 3,493,806

DUAL-BEAM INCANDESCENT LAMP 2 Sheets-Sheet 2 Filed Feb. 23, 1967 FIG.5

HAN

United States Patent 3,493,806 DUAL-BEAM INCANDESCENT LAMP Thomas Antonius Cornelis Jacobs, Victor Rosallie Note]- teirs, and Johannes Rijnders, Emmasingel, Eindhoven, Netherlands, assignors to US. Philips Corporation, New York, N.Y., a corporation of Delaware Filed Feb. 23, 1967, Ser. No. 618,156 Claims priority, application Netherlands, Mar. 19, 1966, 6603641 Int. Cl. H01k 1/26, 1/30 US. Cl. 313113 9 Claims ABSTRACT OF THE DISCLOSURE The invention relates to an incandescent lamp for use in car lights, the tubular bulb of which lamp comprises a main filament, and a dipping filament, the latter being surrounded by a screen extending, in planes transverse to the axis of said filament, through an angle of about 165 to about 180 around said axis. Such lamps are known. Usually the screen is formed by a separate structural element, arranged inside the bulb around the filament.

There are also known iodine lamps in which two filaments are arranged. Iodine lamps, usually termed halogen incandescent lamps have the advantage as compared with other incandescent lamps that for a given power consumption and for a given lifetime they have a considerably greater light output. These factors play a special role in car lighting, since the quality of illumination is highly conducive to the safety required in trafiic. With the use of halogen lamps for car lights, due to the higher light output, however, the requirements as regards avoiding a dazzling effect of the dipped beam become even more stringent. Therefore, there is a need for a halogen incandescent lamp for car lights comprising two filaments, one of which cooperates with a screen, for replacing the conventional two-filament lamps in car lights hitherto employed.

The present invention relates to a two-filament halogen incandescent lamp which by a special choice of the bulb diameter and by a particular disposition of the screen co-operating with the dipping filament, provides the prescribed sharp boundary of the dipped beam, while its specific light output is high and its lifetime is comparatively long. For this purpose the halogen lamp according to the invention is characterized in that the mainly cylindrical bulb of the lamp has an outer diameter of 8 to 14 mms. and the screen co-operating with the dipping filament substantially coincides with the local or interior surface of the bulb wall.

The invention provides a halogen two-filament lamp of comparatively simple construction. Since the screen substantially coincides with the local bulb wall, the prescribed diameter of the bulb provides the advantage that the boundary of the dipped beam cut by the edge of the screen is very sharp. It should be clarified, that with the conventional dimension of the reflectors of car lights, the focal distance being usually about 30 mms. the distance of the 3,493,806 Patented Feb. 3, 1970 axis of the dipping filament from the edge of the screen marking the boundary as has been shown by experiments, has to be about 4 to 7 mms.

A preferred embodiment of the halogen lamp according to the invention is characterized in that the surface of the screen co-operating with the dipping filament coincides substantially with the local outer face of the bulb wall. This provides the advantage that it is not necessary to arrange the screen inside the relatively small lamp bulb. When the screen is arranged on the outer side, the material of said screen can be chosen much more freely. It is then not necessary to take into account physical or chemical reactions likely to occur between the parts inside the lamp and the material of the screen during the operation of the lamp. A comparatively bulky separate screen inside the lamp could adversely affect the effect of the halogen cycle. When the screen is applied in the form of a thin layer of paint to the outer side of the bulb, the influence of the screen material on the halogen cycle need not be considered. The desired optical effect may, of course, also be obtained by a screen formed by a structural part separate from the lamp and bearing on the relevant part of the outer wall of the bulb, instead of a screen applied directly to the bulb-wall, as described above. Such a screen may be supported by the lamp itself or the reflector may be constructed accordingly, so that the screen is supported by the reflector.

As is the case with known two-filament lamps of the kind comprising a built-in screen, also with the lamp according to the invention, attention should be paid to the requirement that along the transverse boundaries of the screen the dipping filament should not emit light rays towards parts of the reflector, from where said rays, subsequent to reflection, could emanate from the search light in any undesirable direction. In the known two-filament lamps this is avoided by providing the screen at the end boundaries with partition-like extensions transverse to the axis of the filament. In an advantageous embodiment of the lamp according to the invention in which the screened filament is substantially located in the axis of the cylindrical bulb, this screening effect can be obtained by arranging inside the bulb space a substantially crescent-shaped screen extending approximately transversely of the bulb axis and viewed in the longitudinal direction of the bulb between the main filament and the clipping filament.

In cases where it is desired, in order to avoid additional metal parts inside the bulb, to omit also the aforesaid crescent-like screen from the bulb space, a further embodiment of the incandescent lamp according to the invention may be used characterized in that the longitudinal axis of the screened dipping filament is arranged eccentrically to the bulb axis.

A further, advantageous embodiment of the lamp according to the invention is characterized in that the screened dipping filament is located between the main filament and the foot of the lamp. This is explained as follows. Owing to the cylindrical shape of the bulb of the lamp according to the invention and owing to the use of a highly loaded filament, which is common practice in halogen lamps, distinct images of the clipping filament are formed inside the bulb by reflection against the bulb wall, which images together form a substantially linear pattern extending approximately along the axis of said filament. This embodiment of the lamp according to the invention will be arranged in a matching reflector so that the screened filament is located between the top and the focus of the reflector. That portion of the linear image pattern which is located between the top and the focus of the refiector then cannot produce dazzling owing to the presence of the screen. The further portion of said pattern, which is located between the focus and the light exit of the reflector will not cause much dazzling, since a com- 3 paratively small part of the relevant light strikes the refiector.

In a halogen lamp according to the invention in which the dipping filament is eccentric to the axis of the bulb,

the desired cut-off of the cross-section of the dipped beam brought about by the screen may, in principle, be achieved by arranging said screen through an angle of more than 180 or smaller than 180 around the axis of the bulb of the lamp. In an advantageous embodiment of the invention the latter possibility is preferred, since then the lightfiux emitted by each of the two filaments of the lamp is affected at the least by the screen.

In a further embodiment of the incandescent lamp according to the invention the surfaces of the portions of the filament stay wires inside the bulb are constructed so as to absorb light; they are, in particular, blackened.

The invention will be described more fully with reference to the drawing in which two embodiments of a halogen incandescent lamp are shown.

FIG. 1 is a top view of one embodiment of a halogen lamp having one pinch, there being provided a crescentlike screen inside the bulb and a screen formed by a layer of paint on the outer wall of the bulb.

FIG. 2 shows the lamp of FIG. 1 in a sectional view taken on the line II-II in FIG. 1. FIG. 2 illustrates diagrammatically the co-operation of this lamp with the parabolic reflector of a car headlight, shown in a sectional view.

FIG. 3 is a cross-sectional view of the lamp of FIGS. 1 and 2 taken on the line III-III in FIG. 1.

FIG. 4 is an elevation view of a further embodiment of the lamp according to the invention, also illustrating the co-operation of this lamp with a parabolic reflector of a car headlight, shown in a sectional View. This lamp comprises a clipping filament arranged eccentrically between the main filament and the pinch of the lamp and located over the bulb axis in the operational state of the headlight as shown.

FIG. 5 is a cross-sectional view taken on the line VV in FIG. 4.

The halogen incandescent lamp shown in FIGS. 1, 2 and 3 comprises a substantially tubular bulb 1, in which a main filament 2 and a dipping filament 3 are arranged. The dipping filament 3 is located in the axis of the lamp and the main filament 2 is positioned transversely of the lamp axis. When this lamp is employed in a parabolic reflector 4 of a car headlight, as shown in FIG. 2, the lamp axis coincides with the axis XX of the reflector, the focal point R; of which is located in the main filament 2.

At one end the bulb 1 is sealed at a point 5 at the other end it is provided with a pinch 6, in which the foils 7 and the ends of the electrode wires 8 and of the stay wires 9, 10 and 11 are sealed. The stay wires 9 and 11 support the main filament 2. The stay Wire 10 supports the crescent-shaped screen 12. The dipping filament 3 is suspended on the stay wire 9 and the screen 12.

The outer side of the bulb wall is provided with a screen 13 in the form of a layer of paint. The screen 13 extends from the screen 12 to the bulb point 5 and is bounded by lines 22 and 23, of which projections in the form of a dotted line are indicated in FIG. 3, said lines being located in planes going through the bulb axis. One of these planes is horizontal, in the operational position of the headlight comprising the lamp, and the other plane is inclined downwards at an angle a. The angle on may be so that in the transverse direction the screen 13 extends through 165.

FIG. 2 illustrates a few light rays for indicating the cooperation between the lamp and the reflector. The rays 14 and 15 emanating from the main filament 2 are emitted by the headlight subsequent to reflection in a horizontal direction. This also applies to the ray 16 from the main filament, since the screens 12 and 13 just leave a free path towards the extreme point 17 of the lower half of the reflector.

A beam 18-19 from the dipping filament 3 leaves the headlight in a downward direction owing to the front position of said filament. None of the rays emanating from the dipping filament 3 lying beyond the range determined "by the angle a can attain the lower half of the reflector. This is prevented by the screens 12 and 13. This is indicated in FIG. 2 by the extreme boundaries 20 and 21 of the rays which could be captured by the lower half of the reflector in the absence of the screens. The screen 13 might be omitted in front of the point of intersection of the boundary 20 with the bulb 1.

The outer diameter of the bulb 1 is greater than 8 mms. and smaller than 14 mms., for example about 11 mms. The boundaries 22 and 23 of the screen 13 are thus located at such a distance from the dipping filament 3 that the images of these boundaries, projected on an imaginary surface located at a given distance in front of the headlight transversely of the axis XX of a reflector 4 having a focal distance of about 30 mms., are very sharply defined. These images formthe boundary of the clipped beam projected on said surface.

The embodiment of the halogen lamp according to the invention shown in FIGS. 4 and 5 comprises a dipping filament 25, arranged eccentrically to the bulb axis ZZ in the centre line YY of the reflector 24. The main filament 26 is arranged transversely of the axis ZZ and includes the focal point F of the reflector in the position of the lamp shown. The dipping filament 25 is furthermore located between the main filament 26 and the pinch 27 of the bulb 28 in the lamp foot (not shown). In the pinch 27 are sealed the foils 29 and the ends of the wires 30 and of the stay wires 31, 32, 33. The dipping filament 25 is supported by the stay wires 31 and 32 and the main filament 26 is supported by the stay wires 32 and 33.

The dipping filament of this lamp is screened only by a layer of paint 34 on the outer side of the bulb wall. This screen extends on either side, to the front and to the rear to an extent such that the light rays from the dipping filament 25 can attain the upper half of the reflector 24 only as far as is permitted for the formation of the known asymmetrical dipped'beam.

The foremost point 35 of the screen 34, indicated in FIG. 4 is located so that the extreme ray 38 of the filament 25 can just not attain the upper half of the reflector 24. This point 35 is furthermore located to the rear to an extent such that the screen 34 does not prevent the rays from the main filament 26 from attaining the upper half of the reflector. The extreme ray 39 is given by way of example. The point 35 is located at the point of intersection of the rays 38 and 39. This is achieved by means of the eccentrical arrangement of the dipping filament 25. In this case an auxiliary screen inside the lamp may be dispensed with.

In the transverse direction the screen 34 is bounded by lines 36 and 37, dotted projections of which are shown in FIG. 5. This figure shows furthermore that the dimensions of the screen may be small owing to the eccentrical arrangement of the filament 25. The distance of the lines 36 and 37 from the axis of the dipping filament 25 lies between 4 and 7 mms. and the diameter of the substantially tubular bulb 28 lies between 8 and 14 mms. Owing to this shape and these dimensions together with a reflector having a focal distance of about 30 mms. a very sharply defined boundary of the dipped beam is obtained.

The dipped beam is produced by the co-operation of the dipping filament 25 with the lower half of the reflector 24 and with a small portion of the upper half of said reflector, determined by the angle B. The angle 3 may be 15, so that the circumference of the screen 34 occupies an angle of Examples of dipped beam rays are shown in FIG. 4

by the lines 40 and 41. Examples of main beam rays are indicated in this figure by the lines 42 and 43, and 44, 4S.

Owing to the position of the dipping filament 25 between the pinch 27 and the main filament 26, that is to say, in the reflector 24 behind the focal point F it is ensured that practically no dazzling can be produced by the substantially linear image pattern formed due to internal reflections in the tubular bulb 28 upon the ignition of the dipping filament. The portion of said pattern located between the focal point of the reflector and the open reflector end will not produce much trouble with respect to dazzling, since only a very small part of the light thereof strikes the reflector.

In the" halogen lamps according to the invention the stay wires (9, and 11 of FIGS. ,1, 2 and 3 and 31, 32, 33 of FIGS. 4 and 5) are preferably provided with a black surface, at least as far as the portion located inside the bulb is concerned. Trouhlesome reflections of the dipping filament on the stay wires are thus avoided.

The drawing shows only two embodiments of the halogen lamp according to the invention. Naturally many variants are possible. The filaments may be arranged otherwise and the screens maybe shaped and disposed diflerently within the scope of the invention. The lamp may comprise more than one pinch.

What is claimed is: v

1. In an electric incandescent lamp, which when oriented to have a central horizontal axis, includes a bulb which cooperates with a parabolic reflector and is disposed adjacent the refiectors closed end, the improvement in combination therewith comprising: a main filament mounted axially within the bulb and positioned at the focal point of the reflector, a dipping filament mounted within the bulb and positioned between the main filament and said closed end and elevated above the main filament, screen means' formed as a coating above the dipping filament on a top exterior surface of the bulb and extending downward on both sides, whereby light from the main filament is projectable oif the reflector as a generally horizontal beam, and certain light from the dipping filament that strikes the reflector forms a downward oriented beam while other light from the dipping filament strikes the screen.

2. A lamp as defined in claim 1 wherein said screen extends downward (a) on one side to an elevation substantially corresponding to that of the dipping filament and (b) on the other side to an elevation about above that of the dipping filament.

3. A lamp as defined in claim 1 wherein the bulb includes iodine for operation as a halogen incandescent lamp.

4. A lamp as defined in claim 1 wherein said bulb is substantially cylindrical and has an outer diameter of about 8 mm. to 14 mm.

5. A lamp as defined in claim 1 wherein the bulb further comprises a base and a plurality of stay wires extending through the base into the bulb for supporting the filaments, said wires having light-absorbing characteristics such as a black surface.

light in combination with an automobile, the lamp fila- V ments being selectively operable for providing a main beam of light and a dipped beam.

7. In an electric incandescent lamp, which when oriented to have a central horizontal axis, includes a bulb which cooperates with a parabolic reflector and is disposed adjacent the refiectors closed end, the improvement in combination therewith comprising: a dipping filament and a main filament mounted coaxially in the bulb, the main filament being between the dipping filament and the closed end of the reflector and positioned at the focal point thereof, a first screen means formed as a coating disposed below the dipping filament on a bottom exterior surface of the bulb and extending upward on both sides and the adjacent end of the bulb, and a second screen means disposed between said two filaments and defining a plane transverse to said central axis and extending from the interior surface of the bulb cut by said plane, upward toward said axis, whereby light from the dipping filament which strikes either screen means is precluded from being reflected upward by the reflector.

8. A lamp as defined in claim 7 wherein said second screen is a crescent-shaped plate extending through an angle of about 165.

9. In a halogen incandescent lamp for automobile lights, the lamp including a tubular bulb having an outer diameter in the range of 8-14 mm., mounted adjacent the closed end of a parabolic reflector, the improvement in combination therewith, comprising a main filament mounted in the bulb and disposed at the focal point of the reflector, a dipping filament mounted along the axis between the main filament and said closed end of the reflector, and a screen formed as a coating on an exterior part of the bulb generally adjacent and above the dipping filament and extending downward.

References Cited UNITED STATES PATENTS 2,795,722 6/ 1957 Burgener et al. 313-113 3,160,777 12/1964 Holcomb 3131l3 3,234,421 2/1966 Reiling 313--114 1,250,030 12/ 1917 Schickerling 313113 X 1,262,395 4/ 1918 Schickerling 3 131 13 X 1,693,672 12/ 1928 Schroeder 3l31l3 2,006,140 6/1935 Honing 313113 X 3,317,772 5/1967 Lindae 313-113 FOREIGN PATENTS 1,081,972 5/1960 Germany. 1,107,337 3/ 1968 Great Britain.

JAMES W. LAWRENCE, Primary Examiner DAVID OREILLY, Assistant Examiner us. 01. X.R. 240-4125; 313 115 

